It is well known to use various mechanical, electrical and electro-mechanical devices to determine the level of material in a tank or container. Mechanical devices include floats, displacers, diaphragms or vibrating elements. Other devices use the specific gravity of the material in order to accurately determine the level of the material in the tank. Also, optical sensors are used as well as conductivity sensing devices. Lastly, microwave sensors have been used for detecting the level of solids or liquids. However, all of these devices are incapable of determining the median level of a fluid in a tank when the fluid is in a state of agitation. Devices are unable to make an accurate measurement when the uniformity of the surface of the fluid is randomly disturbed.
The disadvantages of the prior technology with respect to the agitation are overcome by the present invention, and improved methods and apparatus are hereinafter described for inexpensively and reliably determining the mean level of a fluid in a tank when the surface of the fluid is agitated. Typically, an expensive, sophisticated microwave transducer module, having a wide band width, is required to avoid the problems so elegantly solved by the present invention. With the aid of the present invention, almost any microwave transducer module can be used.